STM32F303RET6 Timer PWM Output Not working as expecte

[samsamm777]

I am trying to configure a PWM output pin. Ive managed to get it working, however the results are not as expected, and i cannot understand whats happening.

Currently my timer clocks are running at 64MHz.

I've setup a timer with the follow values, and it works in producing a 10kHz PWM. The prescalar being 64, should give a frequency of 1MHz. As 64/64=1. Then the Period being 100 should be freq/100 resulting in 0.01MHz. Which is 10kHz. This pwm shows up perfectly on my oscilloscope.

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 64-1;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 100-1;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

However if i change the Period value to 10-1, i would expect a PWM of 100KHz. However I dont get a PWM signal any more. The signal just goes HIGH, and does not change.

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 64-1;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 10-1;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim1.Init.RepetitionCounter = 0;
  htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

What am I doing wrong?

[waclawek.jan]

Read out and check/post content of the TIM and relevant GPIO registers.

You don't use interrupt triggered by this timer, do you?

JW

[samsamm777]

Would you mind please explaining how I can do that? Sorry, im new to STMCubeIDE

[waclawek.jan]

I don't use CubeIDE. There is a peripheral registers​ view there somewhere.

​JW

[samsamm777]

@Community member​ No im not using interrupt for the timer

[Javier1]

Are you using the PWM mode? or just using the timer interrupt to toggle some gpios

[samsamm777]

Ive found the TIM1 registers. This shows the values during runtime. This setup is currently just giving a HIGH signal on the output.

[waclawek.jan · Accepted solution]

CCR1 > ARR, i.e. CNT never reaches CCR1 thus can't "compare match" thus change output level.

JW

PS. Generally it's more useful to display registers in hexadecimal.

[samsamm777]

Ah! so CCR isnt a percent. I was imagining it as the duty cycle percentage. But its not, its purely a count. So I need to calculate the value as a percentage of ARR.